A pulsed periodically poled lithium niobate optical parametric oscillator operating in a cavity with a grazing-incidence grating configuration was used for sensitive and precise measurement of trace quantities of methane in nitrogen by photoacoustic spectroscopy with a novel differential photoacoustic detector. A sensitivity of 1.2 parts in 10<sup>9</sup> by volume of methane was obtained in direct calibration measurements (not extrapolated). With this apparatus, <i>in situ</i> measurement of the methane concentration in ambient air under atmospheric conditions was demonstrated.
© 2002 Optical Society of America
András Miklós, Chin-How Lim, Wei-Wei Hsiang, Geng-Chiau Liang, A. H. Kung, Andreas Schmohl, and Peter Hess, "Photoacoustic Measurement of Methane Concentrations with a Compact Pulsed Optical Parametric Oscillator," Appl. Opt. 41, 2985-2993 (2002)